The present invention relates to a liquid crystal display device, and, more particularly, to a so-called partial transmission type liquid crystal display device.
A so-called partial-transmission type liquid crystal display device is a small-sized liquid crystal display device typically used for a mobile phone, for example; and, images on a display surface of this display device are recognized with the use of natural reflection light from the sun or light produced by an incorporated backlight, when necessary.
The display device has a pair of transparent substrates which are arranged in an opposed manner, while sandwiching a liquid crystal therebetween. On a liquid crystal surface side of one transparent substrate, pixel regions are defined by regions which are surrounded by gate signal lines extended in the y direction and arranged in parallel to the x direction and drain signal lines extended in the x direction and arranged in parallel to the y direction. A thin film transistor, which is driven by a scanning signal from one gate signal line, is provided in each pixel region, along with a pixel electrode to which a video signal is supplied from one drain signal line through the thin film transistor. This pixel electrode is, for example, made of a transparent material, such as ITO (Indium-Tin-Oxide).
On the liquid crystal side of the other transparent substrate, an electric field is generated between the pixel electrode and a counter electrode made of a transparent material commonly formed on each pixel region, and the optical transmissivity of the liquid crystal in the pixel regions is controlled by the electric field.
With respect to the respective pixel regions, by providing reflectors made of, for example, metal layers in approximately half of these regions, it becomes possible to give the liquid crystal display device a function which enables it to generate a reflection-type display at portions where the reflectors are provided and a function which enables it to generate a transmission-type display at portions where the reflectors are not provided.
The constitution of this type of liquid crystal display device is disclosed in detail in, for example, Japanese Patent Laid-open No. 101992/1999 and Japanese Patent Laid-open No. 242226/1999.
However, the liquid crystal display device having such a constitution has a complicated structure and requires a large number of man-hours for fabrication; and, hence, it has been often pointed out that the cost thereof is excessive.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a liquid crystal display device which can reduce the fabrication steps and thereby simplify the fabrication method thereof.
A typical aspect of the invention disclosed in the present application is as follows.
That is, a liquid crystal display device according to the present invention is substantially characterized in that, on each pixel region at a liquid-crystal side of one of the respective substrates which are arranged in an opposed manner, while sandwiching a liquid crystal therebetween, there are provided a thin film transistor, which is driven by a scanning signal from a gate signal line, a pixel electrode to which a video signal from a drain signal line is supplied through the thin film transistor, and a capacity element which is formed between the pixel electrode and a holding capacity electrode.
The capacity element is formed such that a semiconductor layer forming the same layer as a semiconductor layer of the thin film transistor, a first insulation film forming the same layer as a gate insulation film of the thin film transistor, the holding capacity electrode, a second insulation film and a metal layer are sequentially laminated from a substrate side, and the semiconductor layers and the metal layer are connected to each other.
In addition, the metal layer is formed as a reflector which occupies a portion of the pixel region, and, at the same time, it is connected to the pixel electrode which is formed above a third insulation film formed in the pixel region, such that the third insulation film covers the metal layer.
In the liquid crystal display device having such a constitution, the reflector is configured as one electrode of the capacity element. This means that the reflector is formed during the forming of one electrode of the capacity element, so that an increase of the man-hours for fabrication can be suppressed or the man-hours can be reduced.